Most previous research on physical activity using Ajzen's Theory of Planned Behavior (TPB) has assessed the generic term exercise rather than the specific behaviors involved in physical activity. TPB variables for six common types of physical activity were obtained from 233 participants. Both affective and instrumental components of attitude were assessed. Except in the case of walking, multiple regression analyses revealed that intentions for each physical activity type were influenced by affective attitude and perceived behavioral control. Behavior, however, was predicted by intentions alone. In comparison with other types of activity, the TPB accounted for modest amounts of variance in both walking intentions and behavior, with attitudes making no contribution to walking intentions. Discussion focuses on the measurement of physical activity and the implications for health promotion of the poor modeling of walking.